MIRROR IMAGE BACKUP SYSTEM

Storage requirements are outpacing developments in backup tape capacity, and tape systems become cumbersome with large quantities of data.

A number of tapes have to be retained in order to give a reasonable coverage of different versions of a given file, and with the high price of tapes this can prove quite expensive.

Disk storage on the other hand is becoming cheaper all the time (now less than £1 per GB).

Mirror image backups work by maintaining a copy of the main server on a backup server. Software at both ends intelligently assesses whether a file has changed, and transfers only the changes required to synchronize the backup version of the file with the version on the main server. Data compression makes this synchronization process even more efficient.

This does away with the need for tapes, and if a problem were to occur, access to the data on the backup server would be virtually immediate.

The backup can also be made to retain all versions of a file that have existed, by renaming existing files, which can be invaluable for legal audit-trails.

SOME REAL-LIFE STATISTICS

Atelier Ten backs up approximately 120GB of live data each night from a combination of Windows and Linux servers to the on-site backup server, which is kept in a fireproof data safe. This typically takes 20 to 30 minutes.

When this is completed, the backup server is in turn mirrored to a remote server off-site via a 500 kb ADSL line. This normally takes less than two hours.

Thus we have not one but two backups taken every night. You can’t be much safer than that!